情态动词 must 的基本用法:
(1) 表示义务、命令或必要,意为“必须” mustn’t 表示禁止,意为“不许、不可以”。
如: Everyone must attend the lecture. You mustn lend it to others.
(2) 表示推测,意为“一定” 一般用于肯定句
如: The light is still on, so he must be at home.
(3) must 开头的疑问句:
肯定回答用 must 否定回答则常用 needn’t(不需要,不必),相当于 don’t have to
— Must I finish the project today? —No, you needn’t.
情态动词 have to 的基本用法:
(1) have to 作为情态动词,意为“必须、不得不”,侧重于客观上的必要 You have to wear sports shoes for gym class.
(2) 基本句式结构: 主语+have/has to+动词原形+其他.
主语+don’t/doesn’t have to+其他.
Do/Does+主语+have to+动词原形+其他 ?
Tony has to play the guitar every afternoon.
Nick doesn’t have to wear a uniform.
Do you have to stay at home on weekends?
情态动词 must 与 have to 的区别:
(1) must 表说话人的主观看法, have to 表客观需要 I must leave at six today. I have lost my pen, so I have to buy one.
(2) must 只有一种形式 have to 有更多的形式:have to, has to, had to, will have to 等 I thought I must go there. He had to look after his sister yesterday.